In general, a thermal transfer printer employs an ink sheet cartridge which eases replacement of an ink sheet, i.e., handling of the thermal printer. In particular, when the thermal printer is configured as a line printer, a wide ink sheet is used.
Typically, an ink sheet cartridge is configured to have an ink sheet supplying core tube and an ink sheet take-up core tube. Each of the ink sheet supplying core tube and the ink sheet take-up core tube is rotatably mounted on a pair of bearing portions of a cartridge frame with detachable spools attached on both longitudinal (i.e., axial) ends of the core tube.
When the ink sheet is exhausted, the take-up core tube that has the used ink sheet rolled therearound and the supply core tube are taken out of the cartridge frame, and a new ink sheet set with a take-up core tube and a supply core tube having a new ink sheet rolled therearound is attached to the cartridge frame.
To exchange the ink sheets, particularly, to load the new ink sheet set as described above is relatively troublesome. A user may not understand how to exchange the ink sheet even if he/she reads an instruction manual, or in a worse case, the user may not finish the exchange operation completely.
To ease such an exchange operation, some image forming devices are configured such that cartridge frames are exchanged with the ink sheet set being accommodated therein. According to such a configuration, it becomes unnecessary for the user to set the ink sheet in the cartridge frame. The user only replaces the ink sheet cartridge with a new one, which significantly eases the operation of the user.
To achieve the above configuration, however, it is necessary that the ink sheet set be securely accommodated in the cartridge frame so that the core tubes do not become disconnected from the cartridge frame. On the other hand, in view of environmental concerns, material categorized disposal of waste is proceeding in various fields, and it is preferable that the ink sheet cartridge is configured such that the used ink sheet set can be separated from the cartridge frame, and further, that individual components constituting the ink sheet set can be separated for disposal. Thus, it is preferable that the cartridge be decomposed easily for disposal.
As discussed above, it can be difficult to disconnect the ink sheet set from the cartridge frame when the cartridges are being exchanged on one hand, while allowing the ink sheet set to be removed from the cartridge frame for disposal (e.g., after the ink sheet has been completely wound up on the take-up core tube) on the other hand.
To fulfill the above-described contradictory requirements, Japanese Patent Provisional Publication No. P2003-300352A discloses an improved ink sheet cartridge, which is configured such that shaft insertion openings are formed on the cartridge, and shaft supporting portions are formed at each opening. When the shaft is inserted in the openings, the supporting portions are deformed in a shaft inserting direction within an elastically deformable range, while when the shaft is removed, the supporting portions deform in the opposite direction beyond the elastically deformable range.
According to such a conventional cartridge, when the shaft is mounted, the supporting portions recover their original shape after the shaft is fully inserted in the openings, and the shaft is supported by the shaft supporting portions. When the shaft is removed, the shaft supporting portions deform to allow the shaft to be removed smoothly. Therefore, after the ink sheet has been used up, the user can take apart the ink sheet cartridge for categorized disposal.
According to the configuration described above, the shaft is supported by the shaft supporting portions, which are elastically deformable. Therefore, depending on how the ink sheet cartridge is handled, the shaft may be disconnected unintentionally.
Further, when the shaft is dismounted, the shaft supporting portions are deformed beyond the elastically deformable range. That is, when the shaft is removed, the shaft supporting portions are plastically deformed, or completely broken. Therefore, once the mounted shaft is dismounted, it is impossible to mount the shaft since the shaft supporting portions cannot support the shaft.